Transporting apparatus

ABSTRACT

A transporting apparatus in which a series of platforms are driven in a closed-loop, the loop including two similar main segments in adjacent horizontal planes, the upper main segment comprising at least a low speed zone, a curved speed-change zone and a high speed zone and the lower main segment comprising a platform return zone. The apparatus may further include a second curved speed-change zone and second low speed zone. Drive means in the low speed zones are by rotary screws in the high speed zones by powered wheels engaging the platforms and in the speedchange zones by linear motors. The apparatus may be used as a loading or unloading station for a high speed conveyor belt.

United States Patent 11 1 Zu i er Jul 24 1973 TRANSPORTING APPARATUS Primary Examiner-Gerald M. Forlenza Assistant Examiner-D. W. Keen [75 I Inventor Zupp'ger Geneve Swltzer' Attorney-Stevens, Davis, Miller & Mosher [73} Assignees Dunlop Holdings Limited, London,

England ABSTRACT [22] Filed; Jul 16, 1971 A transporting apparatus in which a series of platforms are driven in a closed-loop, the loop including two simi- [211 Appl' l63217 lar main segments in adjacent horizontal planes, the upper main segment comprising at least a low speed [30] Foreign A lic tion P i it D t zone, a curved speed-change zone and a high speed July 17 1970 Switzerland 10911/70 and the lower main Segment cmprising Plat form return zone. The apparatus may further include a 52 U.S.Cl. ..104/25, 198/110 Second curved speed-Change 10m and Second 10W [51] Int. Cl. 865g 23/32 speed Zone' Drive means in the low speed Zones are by [58] Field of Search 104/25, 148 LM, 134, rotary screws in the high Speed by P 198/16 Ms 110 wheels engaging the platforms and in the speed-change zones by linear motors. The apparatus may be used as [56] References Cited a loading or unloading station for a high speed con- UNITED STATES PATENTS 3,580,182 5/1971 Bouladon 104/25 17 Claims, 22 Drawing Figures 3,465,689 9/1969 Ayres 104/25 3,583,325 6/1971 Melin 104/25 PATENTEDJULZMQYS 3 747, 535

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PATENTED 3 747. 535

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SHEET USUF 15 FlGb.

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1 TRANSPORTING APPARATUS The present invention relates to transporting apparatus, such as is used for conveying passengers or goods between points of the type in which the loads being conveyed are loaded onto a low-speed conveyor and subsequently travel on a high-speed conveyor.

An apparatus of this type is disclosed in British Patent No. 1,034,969 in which is described a platform conveyor in which the means for driving the platforms over the various points of the circuit consist firstly of an endless train of screws hingedly connected to one another in succession and disposed along the path followed by the centre of gravity of each platform over the circuit, and secondly of a finger secured underneath each platform and projecting into the thread of the train of screws, such screw serving to bring this train into positive engagement with each platform. In the acceleration and deceleration zones of the circuit described in this patent, the corresponding portion of the screw train has a pitch which respectively increases from the entry end to the exit of the acceleration zone or decreases in the case of a deceleration zone, this screw train portion being rotatably driven by a motor coupled to one end of the portion in question.

This apparatus is however subject to relatively major drawbacks that are inherent to its structure of a purely mechanical nature, some of these drawbacks tending to render the useof this particular form of apparatus awkward or even dangerous, particularly if it is intended for the public transport of people.

in this connection, the safety of the people being conveyed on the platforms is dependent to a very large extent on the continuity of the moving band formed by the platforms, particularly in the acceleration and deceleration zones of the circuit. Such continuity is directly dependent firstly on the machining accuracy of the drive screws and of the platform elements with which these screws are meant to come into engagement, and secondly on the accuracy with which all of these parts are assembled. Under these conditions, it will be appreciated that the production and installation costs of an apparatus of the kind described in the patent can be relatively high. The same applies also to the maintenance costs.

Furthermore, since this is a solution which is wholly mechanical, clearly the various members involved in driving the platforms, in whatever part of the circuit, will be subject to a degree of wear whichwill become more and more pronounced in the course of use of the apparatus in question. such wear being liable to give rise to sufficiently large mechanical play to cause the platforms to move apart in unexpected manner, or even partial jamming, which can lead to decelerations that are particularly dangerous for passengers, in particular for chilren, elderly people and the infirm. Suchdrawbacks can also make themselves felt in the transport of goods, in particular goods of a relatively fragile nature. Further the existence of mechanical play in the described installation can be the source of noise and of platform vibration of an intolerable level for users and, in general, for people and even equipment in the surroundings.

it should further be pointed out that, with the cited apparatus, a break in one of the screws leads to an immediate stoppage in the driving action for a relatively large number of platforms and hence to a deceleration of all of the platforms of the circuit, and such a deceler ation could even be very abrupt if the load being transported by the platforms that are effected by a drive failure is particularly great or if these platforms are those that are momentarily moving over the acceleration or deceleration zone, respectively, of the circuit, where the resistive forces acting on the platforms are among the largest. The particularly serious consequences that can be caused to the goods or people being transported and the importance of the material damage that such jerks could cause will readily be appreciated, whether it be in the upstream part or in the downstream part of the circuit in relation to the platforms that are momentarily blocked.

A final drawback of the apparatus described in UK, Patent No. 1,034,969 lies in the relatively large amount of space occupied by this apparatus, in particular as regards the part thereof which serves to recycle the platforms that successively leave the unloading section and move towards the loading section, this being the circuit portion over which the platforms travel whilst being recycled and which is practically co-planar with the loading, acceleration, deceleration and unloading portion of the circuit.

It is one object of the present invention to obviate some of the above drawbacks.

According to one aspect of the present invention a transporting apparatus comprises a series of transport platforms intended to travel over a closed circuit having a low speed zone, a high-speed. zone, an intermediate speed-change zone between the low and high-speed zones, the speed change zone being in the form of a curve and the cosine of the angle between tangents at the two ends of the curve corresponding to the ratio of the platform speeds in the low-speed and high-speed zones, and a platform-return run curved at least in part as the speed change zone, wherein the circuit comprises a stretched-out loop comprising firstly, two main segments which are contained, one in a first horizontal plane and the other in a second, subjacent, horizontal plane, and secondly two secondary segments which connect the ends of the said main segments to form the closed circuit, the segment in the upper main segment of the loop comprising at least the said low, high and speed-change zones of the apparatus and the segment in the lower main segment of the loop comprising at least the curved part of the platform-return run.

According to another aspect of the invention the upper main segment ofthe loop comprises an addi-,

tional low-speed zone and an additional speed-change zone between the high'speed zone and the additional low-speed zone, the said additional speed change zone being in the form ofa curve and the cosine of the angle between tangents at the ends of the curve corresponding to the ratio of the platform speeds in the high-speed and additional low-speed zone, and the lower main sgement of the loop comprising the return run of the con veyor comprises low-speed end zones one at each end of the segment, a high-speed central zone and two curved speed change zones, one between each zone and the high-speed zone, each being curved as the speed change zones in the upper main segment.

The transporting apparatus is preferably provided with means on each platform enabling detachable, edge-to-edge, hooking engagement with the adjacent platforms, and control means are provided for controlling said hooking means, adapted to engage said hooking means for as long as the platforms move along the main segments of the circuit loop and to relase the platforms from hooking engagement when travelling over one or other of said secondary segments of said loop.

Preferably also the platforms may be driven over the closed loop by means comprising in the speed change zone, a succession of linear motors whose stators are disposed to one side at least of the plane of motion of the platforms, along the path followed by the centres of gravity of these platforms, and whose armatures are formed by at least one metallic mass associated with each platform, in the terminal portions of each main segment of the loop a pair of rotary screws extending on opposite sides of the path followed by the centres of gravity of the platforms, in a plane parallel to the plane of motion of the platforms and over a set length from the end of this main segment, the thread of each screw receiving a projecting element on each platform when the platform reaches the entry end of the screw, and axially pushing the projecting element and the platform towards its exitend, a driving device being provided for the screws, and over the other portions of the said main segments of the loop, a driving mechanism engaging with the platforms in at least a portion of each end of the segments.

The driving mechanism may comprise a set of rubber tyred wheels some of which are powered at least some of which are provided with braking means.

Synchronising means may be provided between the various pairs of screws and the driving mechanism as .required.

Another aspect of the invention provides a conveyor system comprising a transporting apparatus and an endless belt moving at a constant speed substantially equal to the platform speed in the high speed zone of the loop wherein the speed-change zone accelerates a load from the low speed to the high speed for transfer from the high speed zone to the endless belt, the path of the high speed belt being curved so as to avoid the additional speed-change zone and the additional low speed zone which decelerates a load transferring from the high speed belt to the high speed zone.

Yet another aspect of the invention provides a conveyor system in which the transporting apparatus provides a two-part high-speed zone one running adjacent to one side of the belt for transfer of loads onto the belt and the following part of the high speed running adjacent to the other side of the belt for transfer of loads from the belt for subsequent deceleration the two parts being connected by a high speed zone running under the belt;

Barrier devices may be provided to move loads onto or off the belt as required.

Further aspects of the invention will be apparent from the following description of one embodiment of the invention, by example only, in conjunction with the diagrammatic drawings in which:

FIG. I is a developed view in side elevation;

FIGS. 2 and 3 are views along II-II and III-III respectively of FIG. 1;

FIG. 4 illustrates, on an enlarged scale, a partsectional cross-section along IV--IV of FIG. 2;

FIGS. 5 and 6 are cross-sections along V-V and Vl-Vl of FIG. 4;

FIGS. 7 and 8 illustrate in elevation and plan the structural features of another detail of FIG. 1;

FIG. 9 is a cross-sectional view along IXIX of FIG.

FIG. 10 is a view in the direction X-X of FIG. 9;

FIG. 11 is a cross-sectional view along XI-XI of FIG. 1;-

FIG. 12 is a view in the direction XII-XII of FIG. 11;

FIG. 13 shows two adjacent platforms in the high speed load carrying position;

FIG. 14 is a view on XIV-XIV of FIG. 13;

FIG. 15 is a view on XV-XV of FIG. 14;

FIG. 16 is a view on XVI-XVI of FIG. 14;

FIG. 17 shows two ajacent platforms in the high speed return zone of the conveyor;

FIG. 18 is a view on XVIIXVII of FIG. 17;

FIG. 19 is a view on XIX-XIX of FIG. 18;

FIG. 20 is a view on XX-XX of FIG. 18;

FIG. 21 shows a conveyor belt to transporter arrangement;

FIG. 22 shows an alternative arrangement to FIG. 21.

The transporting apparatus illustrated in FIGS. 1, 2 and 3 is more particularly intended for the loading of goods or people on to a transporting band 1, of which only a segment is visible in the drawing, and for unloading these goods or people off this band. This band segment moves in a horizontal plane, it is rectilinear over part of its length and is slightly curved at its right-nand end, in the drawing, so as to move sufficiently far away from the exit of the transporting apparatus.

This transporting apparatus consists of a series of platforms 2a, 2b, 2c. 2m, 2n, etc., moving in joined position over a circuit defined by two guide rails 3 and 4. These rails each form a stretched out loop having two main segments, 3a and 3b, and 4a and 4b, respectively, and two secondary segments, 30 and 3d, and 4c and 411, respectively. The main segments 3a and 4a are contained in a common horizontal plane, the same applies to the segments 3b and 4b, the plane con taining these segments being however situated underneath the plane of segments 3a and 4a. The segments 3c and 4c, and 3d and 4d, respectively, are each of semi-circular shape and are respectively contained in first and second vertical planes that are parallel to each other.

As will be observed from FIG. 2, each of the segments 3c and 4c of the guide rails 3 and 4 comprises five parts A, B E, of which three, A, C and E, are rectilinear whereas the other two B and D, form a curve, i.e. a segment of a parabola.

Similarly, the lower segments 3b and 4b of rails 3 and 4 also comprise five parts A, B, ,E', of which those bearing the references A, C and E are rectilinear whereas parts B and D have a curved outline.

As is known, in particular from the already mentioned U.K. Patent No. 1,034,969 the rectilinear parts of the circuit over which travel the platforms of the illustrated transporting apparatus are those over which these platforms move at constant speed whereas the curved parts, e.g. part E or part B, are those over which these platforms are gradually accelerated or are decelerated. In the present case, the,platforms 2a, 2b, 2c etc. are accelerated when they are being driven over parts B and D of the circuit of the apparatus and are decelerated when they move over parts D and B of this circuit. It should still be pointed out that the parts C and C of the circuit are those over which the platforms move at the greatest constant speed, parts A, E, 3d-4d,

E, A, 3c-4c, being those over which the platforms move at the lowest constant speed.

Since the illustrated transporting apparatus is intended to accelerate goods or people for loading on to the transporting band 1, or to decelerate them, once unloaded from the band, the segments 3a and 4a of rails 3 and 4 are contained in the same plane as that of motion of the band and are parallel to the axis of the rectilinear part thereof. Moreover, the speed at which the platforms move over the circuit part C is identical to the speed V V of the transporting band 1. Over the circuit part A, as also over the part A, and over that formed by the segments 3c and 4c, the speed of motion of the platforms has a value equal to V,,, less than V. The same applies over the circuit parts E and E' as well as over the intermediate part thereof constituted by the secondary loop segments 3d and 4d formed by the two rails 3 and 4. This speed V is chosen to be sufficiently low to enable easy access of the users or of the goods on to part A of the circuit, or to enable unloading of these users or goods from part B of this circuit.

In the example illustrated in the drawing, the ratio of speeds V/V, is equal to 3.5:1; it can of course be less than this value or in other cases greater than e.g. 5.1. Since moreover, it is desired that the acceleration or the deceleration of the loads being transported by the platforms be uniform,the path imposed by the rails 3 and 4 in both part B and part D ofthe circuit is parabolic and the axes of entry into part B and of exit from part D, respectively, which are parallel to the rails 3 and 4 in parts A and E thereof, respectively, form with the axis of motion of the band an angle (b such that cos 4;, V= l/3.5 0.286.

, The particular choice of acceleration or deceleration law for the loads is essentially governed by considerations of safety and comfort. The shape of the path followed by the platforms during accelration or deceleration is of course dependent on this law. These imperatives clearly do not apply as regards the acceleration and deceleration of the platforms moving over the lower part of the loop formed by the rails 3 and 4 since the platforms then travel empty, thus explaining the particularly abrupt deviation thatis imposed on the platforms over part B and over part D of the circuit.

v Viewed from the angle of accelerating up to a speed V the loads coming on to the apparatus at a speed V,,,

less than V, or from the angle of decelerating these loads from the speed V to the speed V,,, the circuit of the apparatus illustrated in the drawing comprises in fact the following four sections: Load acceleration A first low speed V section formed by the circuit part A; a second, high speed V, section formed by the lefthand portion of part C; a third section for accelerating the platforms from V, to V formed by part B; a fourth, platform recycling, section formed by the remainder of the circuit. Load acceleration A first, high speed V, section formed by the straight portion of part C; a second, unloading, low speed V section formed by part E; a third, platform deceleration, section formed by part D; a fourth, load recycling, section formed by the remainder of the circuit.

This consideration leads us to point out that it would clearly be possible, in a constructional variant not shown in FIGS. 1 to 3 to cut the transporting apparatus forming the subject of FIGS. 1 to 3 into two separate parts of which one would essentially serve to accelerate loads and the other to decelerate loads, which parts could of course be sited at locations far removed from each other; (some arrangements will be described below).

As will in particular be observed from FIG. 2, each of the platforms 2a, 2b, 2c, 2m etc. has in plan, the shape of a trapezium of which one of the small sides, here that indicated by the reference a in the case of platform 2a (FIG. 2), forms with one of the two parallel sides, here the side b, an acute angle a such that a 11/2 if 1r, is the angle lying between the two vectors V and V,, and defined by the already mentioned relationship; cos 1b,, V. i

Each platform is formed by a segment from a shaped structural member, of substantially rectangular crosssection, which is partly hollowed out internally and which is for instance produced by extrusion (FIG. 4). On its top surface, each element is lined with a plate 5 from which project a series of parallel ribs 5a for providing the users or the goods loaded on the platforms with sufficient lateral support. It should in this connection be pointed out that, at the entry of circuit part A as also at the exit of circuit part E, the transporting apparatus according to the invention further providesa comb 6 for facilitating the loading and unloading, respectively, of the loads. Only a very small part of this comb is shownin FIG. 4, where one of its teeth is seen to project between two ribs of a plate 5. Further details of the conveyor grooves are disclosed in copending applicattion Ser. No. 143,989 filed Mar. 17, 1971.

On its underneath surface, each platform is provided with two annular supports 7 (FIG. 4) which are located, one, near the longitudinal edge b of the platform (see FIG. 2) and the other, near the second longitudinal edge of the latter, the distance between the axes of these two supports, projected on to one or other of the parallel edges of the corresponding platform, being equal to the distance between the axes of symmetry of the rails 3 and 4 along, for instance, part A of the circuit.

In each of the supports 7 with which are provided the various, platforms'is mounted a turret Sbodily associated with the upperpart of a trolley 9 provided with two grooved rollers g, and g by means of which each trolley 9 rolls over the outer face of the corresponding rails 3 or 4. On the rotational axis of each of these rollers, a, and a respectively, there is pivotally mounted a lever l, and 1-,. respectively carrying at its free end a second roller, g and g4 respectively, rotatably mounted on the corresponding lever and moving in contact with the inner face of will! or 4. It will moreover be observed that the free end of the levers I or I, carries two buffers u and u-,, and 14*, and u*;, respectively, the terminal portion of which extends to a distance from the pivotal axis of rollers 3 and g.,, respectively, which is greater than that of the radius of these rollers thereby to avoid contact between the rollers belonging to the trolleys of one of the platforms and the rollers 3 of the trolleys on the preceding platform, in particular when these platforms are travelling over the two secondary segments 3c and 4c, and 3d and-4d, respectively, of the loops formed by the rails 3 and 4. Further, each trolley is provided at each of its ends with a buffer x, or x respectively by means of which the trolleys of each platform come into contact with the corresponding trolleys of the adjacent platforms, in particular when all of these platforms are moving over the secondary segments 3c, 40, 3d and 4d mentioned earlier.

Each platform of the transporting apparatus is capable of being hooked to an adjacent platform by means of two hooking mechanisms (which are further described in U.S. Pat. No. 3,695,183 of Oct. 3, 1972 each comprising a male portion and a female portion, the components of one of these mechanisms being visible in FIGS. 5 and 6.

When the platforms are moving for instance over the segments 30 and 4c of the guide rails 3 and 4 over part A of the circuit, the longitudinal axes of the two parts of these mechanisms extend, one, in the sectional plane IV-IV (FIG. 2), as shown in FIG. 4 and, the other, in a plane parallel to the first. As can be seen in the drawing, these two planes pass respectively through the pivotal axes of the'first and second trolleys 9 carried by each platform.

The various platforms are each formed on their longest side faces with two longitudinal grooves p and p the cross-section of which is cylindrically shaped with a common diameter. It is these grooves that are anchored the first and second portions, respectively, of each of the hooking mechanisms.

The description which will now follow only relates to one of these mechanisms but it also applies to the other. It should be read with the assistance of FIGS. 4 and 6.

In the groove p, of each platform is mounted a socket member 10 which is provided on its outer surface with a liner of anti-friction material 11 and which is formed with a transverse passage 10a into which is inserted, and secured by a pin 12, the end 13a of a tie-rod 13. By virtue of the liner 1], the socket member 10 may not only be pivoted in the housing p, but can also be made to slide axially therein; it is of course also possible to keep the socket member stationary and to move the platform angularly or axially in relation to this socket member.

The tie-rod 13 has a portion 13b, of rectangular cross-section, adjacent a shoulder 13c, and, at its free end, an abutment 13d. Between these two elements, i.e. the shoulder and the abutment, the tie-rod is of cylindrical outline.

In the groove p of eachplatform are secured two substantially cylindrical components 14A and 148 which are disposed in substantially co-axial relationship and which define between themselves a space 15.

It is to be noted that the arrangement of the components 14A and 14B inside the groove p is such that the longitudinal axis of symmetry of the space 15 lies substantially parallel to the longitudinal axis of the trolley 9 (FIG. 4), when the latter is oriented at right angles to the longitudinal sides of the corresponding platform.

In component 14B is bored a cylindrical passage 16 (FIG. 6) opening in the space 15. The component 14A is formed with a cylindrical recess 17 (FIG. 6) opening in the space 15, which extends co-axially with the passage 16 and which has the same diameter as this passage. This passage and this recess are intended to receive first and second pivot members 18 and 29, respectively, which are secured in diametrically opposite positions to the side face of a socket member 20.

In the component 14A there is also cut a slot 14* (FIG. 5) in which is slidably mounted a rectangular welded-on" extension of a locking bolt 22, such that the bolt 22 may slide guided by the extension in the slot.

To one end of the bolt 22 is welded a stop member 24 which engages a similar step 25 in axial alignement with the first step to prevent excessive movement. A spring 26 is mounted over and abutting the two steps to bias the bolt 22 to one side of its movement and thus take up a locking position (indicated in FIG. 5), the unlocking action taking place by exerting a thrust, from left to right in the drawing, on a roller 27 pivotally mounted at the end ofa lug 22b on the locking bolt 22.

To ensure that the locking bolt will be held on the component 14A, the locking bolt is provided with a longitudinal slot 22d (FIGS. 5 and 6) between the edges of which extends a projecting element 28 solid with the component 14A which has provided a rectangular head 28a larger than the slot 22d.

As will be observed from FIG. 5, the locking bolt is formed at its left end with a notch of substantially rectangular shape 22e. This notch is defined by two teeth 22fand 22g and its width is slightly greater than that of the rectangular portion 13b of rod 13. Thus, as soon as two platforms, e.g. platforms 2a and 2b, are sufficiently near each other, or in contacting relationship, as is the case with two platforms in FIG. 4, and if nothing restrains the action of the spring 26, the rod 13 of one of the platforms, here that of platform 2a, is fully inserted inside the platform 2b, by sliding the socket member 20 mentioned earlier; further, if nothing restrains the action of the spring 26, the locking bolt 22 that is fixed on the platform 2b engages round the rectangular portion 13b of the rod 13 that is carried by the other platform, 2a. It follows therefore that if platform 2b is driven from left to rightin the drawing (FIG. 4), this platform also draws with it platform 2a, the abutment 13c on the rod 13 coming to bear on the locking bolt 22 of platform 2a.

When the locking bolt is moved out of its locking position platform 2b releases itself from platform 2a, and, if only the first is driven, it moves away from this platform at most by a length limited by contact of the abutment 13d of rod 13 (FIGS. 4 and 6) with one end of the socket member 20. As will be observed, the platforms of the transporting apparatus according to the invention are able to occupy two separate relative positions, one in which the platforms are close together and the other in which the platforms are remote from each other.

When the platforms travel over the upper main segment of the circuit loop, which is observed for the conveyance of loads, they are in close relationship soas to form a continuous band. This is also the case when these self same platforms move over the lower main segement of the circuit.

The platforms are however in spaced-apart relationship when they are travelling over the two secondary segments of the circuit (parts 3c and 4c, 3d and 4d of rails 3 and 4). FIG. 4 shows the relative position of the platforms over these circuits segments.

For the platforms to be able to occupy the position shown in FIG. 4, it is essential that the locking bolts 22, for hooking the platforms together two by two, he opened. To this end, the illustrated transporting apparatus comprises a first pair of ramps for actuating the locking bolts 22 of the two hooking mechanisms connecting each platform to a neighbouring platform, these ramps extending along the segments 3c and 4c of 

1. Transporting apparatus comprising a series of transport platforms intended to travel over a closed circuit having a lowspeed zone, a high-speed zone an intermediate speed-change zone between the low and high-speed zones, the speed change zone being in the form of a curve and the cosine of the angle between tangents at the two ends of the curve corresponding to the ratio of the platform speeds in the low-speed and high-speed zones, and a platform-return run curved at least in part as the speed-change zone, wherein the circuit comprises a stretched out loop comprising, firstly, two main segments which are contained one in a first horizontal plane and the other in a second, subjacent, horizontal plane, and secondly two secondary segments which connect the ends of said main segments to form the closed circuit, segment sgement in the upper main segment of the loop comprising at least the said low, high and speed-change zones of the apparatus and the segment in the lower main segment of the loop comprising at least the curved part of the platform-return run, the platforms being driven over the closed loop by means comprising: in the speed-change zones a succession of linear motors whose stators are disposed to one side at least of the plane of motion of the platforms, along the path followed by the centers of gravity of these platforms, and whose armatures are formed by at least one metallic mass associated with each platform, in the terminal portions of each main segment of the loop a pair of rotary screws extending on opposite sides of the path followed by the centers of gravity of the platforms, in a plane parallel to the plane of motion of the platforms and over a set length from the end of this main segment, the thread of each screw receiving a projection element on each platform when the platform reaches the entry end of the screw, and axially pushing the projecting element and the platform towards the exit end of the screw, a driving device being provided for the screws; and over the other portions of the said main segments of the loop, a driving mechanism engaging with the platforms in at least a portion of each end of the segments.
 2. Transporting apparatus according to claim 1 wherein the upper main segment of the loop comprises an additional low-speed zone and an additional speed-change zone between the high-speed zone and the additional low-speed zone, the said additional speed change zone being in the form of a curve and the cosine of the angle between tangents at the ends of the curve corresponding to the ratio of the platform speeds in the high-speed and additional low-speed zone, and the lower main segment of the loop comprising the return run of the conveyor comprises low-speed end zones one at each end of the segment, a high-speed central zone and two curved speed change zones, one between each end zone and the high-speed zone, each being curved as the speed change zones in the upper main segment.
 3. A conveyor system comprising a transporting apparatus according to claim 2 and an endless belt moving at a constant speed substantially equal to the platform speed in the high-speed zone of the Loop wherein the speed-change zone accelerates a load from the low speed to the high speed for transfer from the high speed zone to the endless belt, the path of the high speed belt being curved so as to avoid the additional speed-change zone and the additional low speed zone which decelerates a load transferring from the high speed belt to the high speed zone.
 4. A conveyor system according to claim 3 wherein a barrier is provided to move loads from the high-speed zone of the zone of the transport apparatus onto the endless belt.
 5. A conveyor system comprising a transporting apparatus according to claim 2 and an endless belt moving at a constant speed substantially equal to the platform speed in the high speed zone of the loop wherein the speed-change zone accelerates a load from the low speed to the high speed for transfer to the endless belt and the additional speed change zone and additional low speed zone are accommodated between the load-carrying and return runs of the endless belt.
 6. A conveyor system according to claim 5 wherein a barrier is provided to move loads from the high-speed zone of the transport apparatus onto the endless belt.
 7. A conveyor system comprising a transporting apparatus according to claim 2 and an endless belt moving at a constant speed substantially equal to the platform speed in the high-speed zone of the loop wherein the high-speed zone runs adjacent to one side of the belt for transfer of loads onto the belt and then passes under the belt and runs adjacent to the other side of the belt for transfer of loads from the belt for subsequent deceleration in the additional speed change zone.
 8. Transporting apparatus according to claim 1 wherein each platform is provided with means enabling detachable, edge to edge, hooking engagement with the adjacent platforms, and control means are provided for controlling said hooking means, adapted to engage said hooking means for as long as the platforms move along the main segment of the circuit loop and to release the platforms from hooking engagement when travelling over the said secondary segments of said loop.
 9. Transport apparatus according to claim 8 wherein the driving mechanism comprises at least one wheel mounted on an axle having driving means for engaging the underside of each of the platforms in turn.
 10. Transport apparatus according to claim 9 including an unpowered wheel for engaging the underside of each platform and braking means for the unpowered wheel.
 11. Transport apparatus according to claim 9 wherein the wheels have rubber pneumatic tires.
 12. Transport apparatus according to claim 8 comprising at least one wheel mounted on an axle having braking means, the wheel engaging the underside of each of the platforms in turn.
 13. Transport apparatus according to claim 1 wherein synchronising means are provided for the various pairs of screws and the driving mechanism.
 14. Transport apparatus according to claim 1 wherein at ambient temperature, the length of the circuit is greater than the length that is effectively occupied by all of the platforms.
 15. Transport apparatus according to claim 14 wherein the pair of screws at the entry of the upper main segment of the loop and the pair of screws disposed at the exit of the lower main segment are kinematically solid with each other, and the pair of screws at the exit of said upper main segment and the pair of screws disposed at the entry of the said lower main segment are kinematically independent of each other.
 16. Transport apparatus according to claim 1 wherein the linear motors are induction motors.
 17. A conveyor system according to claim 16 wherein a barrier is provided to move loads from the high-speed zone of the transport apparatus onto the endless belt. 